Isolation and structural elucidation of a novel type of ganglioside, deaminated neuraminic acid (KDN)-containing glycosphingolipid, from rainbow trout sperm. The first example of the natural occurrence of KDN-ganglioside, (KDN)GM3.

Rainbow trout sperm contained almost exclusively monoanionic ganglioside fraction as a major acidic glycosphingolipid. Two monoacidic gangliosides were isolated and purified in this study and designated as sperm ganglioside 1 and 2 (sg-1 and sg-2). The two gangliosides, sg-1 and sg-2, contained the same neutral sugars, galactose and glucose in molar ratio of 1:1 and no GalNAc except for the presence of N-acetyl-neuraminic acid (NeuAc) in sg-1 and deaminated neuraminic acid (KDN; 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid) in sg-2. The complete structures of these gangliosides were determined by a combination of methylation analysis, fast atom bombardment mass spectrometry, 400-MHz one- and two-dimensional 1H nuclear magnetic resonance spectroscopy, fatty acid analysis, and endoglycoceramidase digestion NeuAc alpha 2----3Gal beta 1----4Glc beta 1----Cer sg-1 [(NeuAc)GM3] KDN alpha 2----3Gal beta 1----4Glc beta 1----Cer sg-2 [(KDN)GM3] where, for both sg-1 and sg-2, the ceramide moieties (Cer) were found to be made up of 4-sphingenine and mainly C16:0 fatty acid (palmitate; 95%) with a minor amount of C24:1 fatty acyl chain (nervonate, 5%). The structure of sg-2 is novel and represents the first example of a new class of gangliosides, i.e. KDN-gangliosides.